The discovery of a novel sulfatase of unusual specificity and the synthesis of isomeric glucosamine sulfates of known structure have led to the discovery that heparin contains a 3-0 sulfated glucosamine residue which is essential for its role as an anticoagulant. The enzyme, which has been partially purified from pooled human urine, is present as several differently charged forms. Many polyanions, including heparin, induce allosteric changes in the structure of hemoglobin. In a study of the effects on hemoglobin of polyanions of controlled size, highly sulfated trehalose and stachyose have been prepared. These compounds have been found to bind with high affinity to hemoglobin-S and strongly decrease its affinity for oxygen. Studies of the effects of these and related compounds on the solubility of hemoglobin-S are being carried out.